/Engine/Source/Runtime/Core/Public/Internationalization/TextLocalizationManager.h
Finds and returns the display string with the given namespace and key, if it exists. Additionally, if a source string is specified and the found localized display string was not localized from that source string, null will be returned.
FTextConstDisplayStringPtr FindDisplayString ( const [FTextKey](API\Runtime\Core\Internationalization\FTextKey) & Namespace, const [FTextKey](API\Runtime\Core\Internationalization\FTextKey) & Key, const [FString](API\Runtime\Core\Containers\FString) *const SourceString ) const